Courtesy of Jack Cook, Woods Hole Oceanographic Institution

As the oil from BP’s Deepwater Horizon accident seeps into Louisiana’s 48,000 acres of wetlands, it’s officially beginning to endanger the habitat and nesting areas of many species of fish, invertebrates and birds. If the problem worsens, it will create insufferable burdens for area fishers and the markets and restaurants they serve. Not to mention, the oil infiltration threatens to decimate New Orleans’ natural first line of defense from devastating tropical storms – and the wetlands already were being recaptured by the sea before the oil rig disaster.

In the most severe scenario, the damage to wetlands isn’t temporary. But hundreds of millions of taxpayer dollars are already being spent on costal resoration efforts, and BP may be pressured into coughing up much more.

Though government and oil-company officials have said BP will pay for damages, putting a price on ruined wetlands isn’t like assessing property damage from hurricanes or faulty levees.

“This is a little different,” said P.J. Hahn, director of coastal zone management for Plaquemines Parish. “You can rebuild houses and highways, but it’s a lot more difficult to rebuild an estuary. That’s a much greater challenge.”

“We could see 50 years of wetlands erosion occurring in a fraction of that time if we don’t act now to re-build these critical natural barriers,” said Paul Harrison of the Enviromental Defense Fund. That could happen because of a combination of factors. First, certain toxic chemicals in the oil can weather away the marsh soils making it more vulnerable to erosion. Second, the oil ruins or seriously compromises the habitat of the myriad small creatures that live in and under the marsh, and which contribute to the stoutness of the land.

For instance, the oil is likely to drive away fiddler crabs, which till the  marshland, allowing needed oxygen to reach grass roots. The grass, of course, holds together the fragile land.

It could take years, if not decades, to assess wetlands damage because of the oil’s tendency to slowly degrade in some marsh areas. To get an understanding of what oil can do to marsh, look back to the big spill of 1969 — but not the accident in Santa Barbara, Calif., that made oil-slicked birds poster-children for environmental degradation. In another disaster that year, a barge crash off the coast of Massachusetts spilled 189,000 gallons of oil off the coast of Cape Cod.

Four decades later, traces of oil can still be found in the  Cape Cod marshes,  even though the amount that spilled is less than the estimated 210,000 gallons being spilled each day since the April 20 explosion.

“You can stick a shovel in the ground today and still smell fuel,” said Christopher Reddy, a scientist at the Woods Hole Oceanographic Institution in Massachusetts, who studies oil spill impacts on coastal environments. “The thought back then was the oil would last for a short amount of time, but instead it took at least seven years before any grass started to grow back.”

Traces of hazardous chemicals in the soil  still keep fiddler crabs from burrowing  to hide from predators, he said. One of Reddy’s graduate students found that in some oily hotspots, the crabs move slowly, “as if they were literally intoxicated from exposure to the residual oil,” wrote Reddy in his institution’s organ Oceanus

This doesn’t necessarily mean the same fate will come to Louisiana. The oil leaking today is not the same as what leaked in the ’69 spill, and every kind has its own chemical composition and personality. Other studies of oil spills near marshes have shown a quick rebound –  one near Portland, Maine, saw its grass grow back in less than a year.

But then there’s the 1974 spill near Buzzards Bay, Mass., which eroded marsh to the point that much of the grass still hasn’t grown back. Once oil gets into the muddy grass, it’s almost impossible to clean it out. Additionally, when the oil settles into the mud, the oily particles can later trickle down to form toxic sediment at the floor below the surface, causing more environmental problems if dredging later occurs.

To track the long-term effects of the Deepwater Horizon spill, the National Oceanic and Atmospheric Association is working with Applied Science Associates of Rhode Island, which is taking samples from a series of locations to set a baseline for future comparison.

“I don’t think there has ever been a large oil spill this close to a very large wetlands area,” says Maurice Spalding, chairman of Applied Science Associates.. “The good news is that much of the toxic compounds will evaporate relatively quickly making the oil [reaching the wetlands] less toxic.”

The cost of damages from geographic and animal loss alone could be way out of reach for BP or the federal government.

The government already is paying a steep tab for coastal erosion – some 2,300 square miles of wetlands gone over the last 75 years. More than a half billion dollars in federal money already had been set aside for coastal restoration, before the spill, in the 2009, 2010 and 2011 budget years.

The state of Louisiana hasn’t been completely successful in its own restoration plans. The federal-state shared Coastal Wetlands, Planning, Protection and Restoration Act, otherwise known as the Breaux Act, is a $60-million-a-year program headed by the U.S. Army Corps of Engineers and involving multiple state departments.

The task force overseeing that spending this year voted to end the biggest coastal project to get underway, the West Bay River Diversion, though it will take until 2011 to abandon the effort. It cost $22 million to create, but there is not enough money to maintain it. Among other things, the project prevents saltwater intrusion into the wetlands by providing a constant outflow of fresh water from the Mississippi River in lower Plaquemines Parish. As the BP leak continues to flow west, the hope is that the diversion will prevent oil intrusion as well. Once closed, it will be yet another spot of vulnerability.

One source of funding that could help these restoration efforts is the Harbor Maintenance Trust Fund, a federal account filled with money from taxes collected on imported cargo on ships. But Congress holds the purse strings on it, and has been appropriating just half to two-thirds of the funds a year, while diverting the rest to its general fund. Legislation was introduced last month with co-sponsorship from Louisiana Sens.  David Vitter, a Republican, and Mary Landrieu, a Democrat, to ensure that in the future all money goes to its intended purposes.

“If there had been more money appropriated, one beneficial use we could have done was marsh restoration,” said Sean Duffy, president of the Gulf States Maritime Association. “This is most important to Louisiana than anywhere else. We can dredge material for the coastline and marshes to help restore the [delta] bird’s foot and look at other areas to divert mud to as well, but until we get more money we can’t change the system.”

Right now, Duffy is keeping busy making sure navigating ships headed into the Southwest Pass aren’t lined with oil. There are workers in place, hired by BP and the Coast Guard to monitor ships and clean them if necessary.

As of today, over 290 vessels are in the seas responding to the spill. BP has also been recruiting local fishers to take their own boats to help skim and lay boom, but the fishers have complained that they are not being offered adequate supplies and equipment to do this.

The major focus now is to keep as much oil as possible out of the marsh. Staging areas have been set up in in thirteen areas between Louisiana and Florida. Over 372,000 gallons of the controversial dispersant solution has been applied to the Gulf and 1.1 million feet of absorbent boom has been deployed. The Deepwater Horizon Unified Command reported May 10 that 3.6 million gallons of oily water had been recovered since the initial leak on April 20. But determining how much has gotten into the marsh will be far more difficult.